Prognostic role of CIP2A expression in serous ovarian cancer.

BACKGROUND: Cancerous inhibitor of protein phosphatase 2A (CIP2A) is an oncoprotein expressed in several solid cancers. Our purpose was to study its role in serous ovarian cancer patients, and the association to clinicopathological variables and molecular markers. METHODS: We collected retrospectively 562 consecutive serous ovarian cancer patients treated at the Helsinki University Central Hospital. We stained tumour tissue microarrays for CIP2A by immunohistochemistry and constructed survival curves according to the Kaplan-Meier method. Associations to clinicopathological and molecular markers were assessed by the χ(2)-test. RESULTS: We found strong cytoplasmic CIP2A immunoreactivity in 212 (40.4%) specimens, weak positivity in 222 (42.4%) specimens, and negative in 90 (17.2%). Immunopositive CIP2A expression was associated with high grade (P<0.0001), advanced stage (P=0.0005), and aneuploidy (P=0.001, χ(2)-test). Cancerous inhibitor of protein phosphatase 2A overexpression was also associated with EGFR protein expression (P=0.006) and EGFR amplification (P=0.043). Strong cytoplasmic CIP2A immunopositivity predicted poor outcome in ovarian cancer patients (P<0.0001, log-rank test). CONCLUSION: Our results show that CIP2A associates with reduced survival and parameters associated with high grade in ovarian cancer patients, and may thus be one of the factors that identify aggressive subtype (type II) of this disease.

Genetic alterations and protein expression of KIT and PDGFRA in serous ovarian carcinoma.

KIT and PDGFRA are receptor tyrosine kinases that can be specifically inactivated by small-molecule tyrosine kinase inhibitors, notably imatinib mesylate. In ovarian carcinoma, expression of KIT and PDGFRA protein has been documented, but the frequency and the molecular background of expression are poorly known. We analysed the expression of KIT and PDGFRA by immunohistochemistry in 522 serous ovarian carcinomas, and mutations of KIT and PDGFRA by denaturing high-performance liquid chromatographyin 125 and 187 serous ovarian carcinomas, respectively. No mutations of KIT or PDGFRA were detected. KIT expression was detected in 12% of carcinomas: low expression in 10% and high expression in 2% of cases. Using normal serous epithelium as a reference, decreased PDGFRA expression was detected in 12% and increased expression in 13% of carcinomas. Both KIT and PDGFRA expression were associated with high tumour grade, high proliferation index and poor patient outcome. By fluorescence in situ hybridisation, no KIT amplification was found in carcinomas with high KIT expression, but two cases showed a relative gain of chromosome 4. In conclusion, no mutations of KIT or PDGFRA were found, but a subset of serous ovarian carcinoma showed overexpression of the proteins, which was associated with aggressive tumour characteristics.

Allelic analysis of serous ovarian carcinoma reveals two putative tumor suppressor loci at 18q22-q23 distal to SMAD4, SMAD2, and DCC.

The distal half of chromosome arm 18q is frequently lost in ovarian carcinoma. To define the putative tumor suppressor locus/loci more precisely we performed allelic analysis with 27 polymorphic microsatellite markers located at 18q12.3-q23 in 64 serous and 9 mucinous ovarian carcinomas. Fifty-nine percent of the serous carcinomas, but only one (11%) of mucinous carcinomas, showed allelic loss at one or more loci (P = 0.018). In serous carcinomas, deletions were found to be associated with tumor grade and poor survival. The highest frequency of losses was detected at the distal part, 18q22-q23. Two minimal common regions of loss (MCRL) were identified at this region: MCRL1 between D18S465 and D18S61 at 18q22 (3.9 cM) and MCRL2 between D18S462 and D18S70 at 18q23 (5.8 cM). At 18q21.1, proximal to the MCRLs, there are three candidate tumor suppressor genes: SMAD4 (DPC4), SMAD2, and DCC. Their protein expression was studied by immunohistochemistry in normal ovarian tissue and serous carcinomas. Lost or very weak expression of SMAD4, SMAD2 and DCC was found in 28, 28, and 30% of serous carcinomas, respectively. Comparison of allelic loss and protein expression status indicated that none of these genes alone could be the target for the frequent allelic loss at 18q21.1. Together, these genes may account for a substantial proportion of the events, but not all of them. Thus, we propose that the frequent allelic loss at 18q is because of the effect of multiple genes, and there is at least one as yet unidentified tumor suppressor gene at 18q residing distal to SMAD4, SMAD2, and DCC involved in serous ovarian carcinoma.

Comparison of serous and mucinous ovarian carcinomas: distinct pattern of allelic loss at distal 8p and expression of transcription factor GATA-4.

Using comparative genomic hybridization (CGH), we have previously demonstrated frequent loss of 8p, especially its distal part, in ovarian carcinoma. To compare the deletion map of distal 8p in serous and mucinous ovarian carcinomas, we performed allelic analysis with 18 polymorphic microsatellite markers at 8p21-p23. In serous carcinoma, loss of heterozygosity (LOH) was detected in 67% of the samples, and the majority of the carcinomas showed loss of all or most of the informative markers. In contrast, only 21% of mucinous carcinomas showed allelic loss, with only one or two loci showing LOH in each sample. In serous carcinomas, LOH was associated with higher grade tumors. Three distinct minimal common regions of loss could be defined in serous carcinomas (at 8p21.1, 8p22-p23.1, and 8p23.1). Expression of a transcription factor gene, GATA4, located at one of these regions (8p23.1) was studied in serous and mucinous ovarian carcinomas by Northern blotting and immunohistochemical staining of tumor microarray. Expression was found to be lost in most serous carcinomas but retained in the majority of mucinous carcinomas. Our results suggest distinct pathogenetic pathways in serous and mucinous ovarian carcinomas and the presence of more than one tumor suppressor gene at 8p involved in the tumorigenesis of serous carcinoma.